1. Field of the Invention
The invention pertains to an improved process for the hydrogenolysis of acetals and ketals of organic hydrocarbons by utilizing a new catalyst system.
2. Description of the Prior Art
Hydrogenolysis of acetals and ketals of organic hydrocarbons has heretofore been accomplished by employing stoichiometric amounts of either halo-alkyl aluminum compounds or mixtures of aluminum halides and lithium aluminum hydride. The extremely flammable nature of these reagents is well-known. The AlX.sub.3 --LiAlH.sub.4 method for the hydrogenolysis of ketals involves the formation of aluminum trihydride, AlH.sub.3, a hazardous compound. While, there are known alternatives to the hydrogenolysis processes, such processes suffer from the production of undesired byproducts and low yields. Furthermore, catalytic hydrogenolysis of acetals and ketals of organic hydrocarbons does not take place over most hydrogenation catalysts under normal hydrogenation conditions, even at relatively high temperatures and pressures.
One report in the literature describes the catalytic hydrogenolysis of certain ketals at moderate temperatures and pressures: Howard, W. L. and J. H. Brown, Jr., J. Org. Chem., 26, 1026 (1961). These authors noted that rhodium was the hydrogenolysis catalyst of choice, palladium much less desirable, while both platinum and ruthenium proved essentially inactive. The ketals studied by Howard and Brown were simple alkyl derivatives, and hence the products were simple ethers and alcohols, with the reaction occurring as shown below: ##STR1## wherein the R groups were with one exception, C.sub.1 to C.sub.4 alkyl groups. Bronsted acids, such as hydrogen chloride, were used to provide the hydrogen ion. These processes required significant amounts of make-up acid.